Our long term objective is to identify the molecular factors responsible for light scattering and opacification of the lens. Light scattering is produced by the formation of high molecular weight aggregates of the lens proteins and by the separation of the lens proteins into coexisting protein-rich and protein-poor phases. The molecular factors responsible for these scattering elements are contained in the form of the fundamental interprotein interaction potential which can be determined from the phase-diagram and equation of state of protein solutions. We shall establish the form of this potential and connect it with the chemical structure of the lens crystallins. This connection will enable us to develop strategies for the rational design of reagents capable of inhibiting the formation of lens opacities. To achieve these objectives, we propose the following Specific Aims: 1. To determine the phase diagrams, the equations of state and the kinetics of aggregation of recombinant native bovine and human gamma-crystallins. 2. To determine the phase diagrams, the equations of state and the kinetics of aggregation of mutant bovine and human gamma-crystallins, obtained by site-directed mutagenesis. 3. To explore the effect of specific covalent and non-covalent modifiers on the phase separation and aggregation of bovine and human gamma-crystallins, so as to identify putative inhibitors of cataract. 4. To develop a theoretical description based on the pairwise interaction between proteins to predict the phase diagram, the equation of state and the kinetics of aggregation of the gamma-crystallins.